The harvesting capacity of a cotton harvester is determined by the capacity of the harvesting unit to remove the cotton from the plant and the capacity of the air system to convey the cotton downstream from the harvesting unit. If the harvester is a cotton stripper equipped with a cotton cleaner, the capacity of the cleaner to process and remove the burs and foreign material from the cotton also affects the overall machine capacity.
The operator can see when the row units are operating at or above capacity by the amount of cotton left on the stalk, and in over-speed conditions, excess cotton will remain. However, a monitor system is required for the operator to determine if the air system and cleaner are running close to capacity. Current cotton strippers have a speed sensor on the top saw of the cleaner. A readout in the cab provides top saw speed which gives the operator an indication of percent of full capacity of the cleaner. If the top saw slows below a predetermined lower speed, an audible alarm and light will be activated to warn the operator that the machine must be slowed to avoid cleaner plugging. Conversely, the readout informs the operator there is additional capacity in the cleaner so machine speed can be increased to gain productivity.
Many cotton material conveying systems include a nozzle pointed downstream in the air duct to induce a vacuum in the lower part of the duct which draws removed material upwardly. Manually adjustable vacuum switches using a spring and diaphragm are available to measure the difference in pressure between the lower portion of the air duct and the cab. When the vacuum falls below the set point as a result of duct capacity being approached or exceeded, the sensor triggers a light and audible alarm to warn the operator to decrease harvester speed. Several problems exist with present vacuum monitoring systems. First, the systems measure the vacuum relative to cab pressure, and cab pressure can vary if the cab air conditioning system blower speed is changed, the cab door is opened, or the cab inlet filter gets plugged. Any such variance requires the operator to reset the sensor for effective operation. Secondly, setting the sensor requires a trial and error approach wherein the operator increases speed until the machine plugs to see if the sensor is set correctly. If the setting is incorrect, the operator must readjust the setting to try to initiate a warning just before the duct blockage condition occurs. The third problem with the current vacuum system is inability of such a system to inform the operator when there is additional capacity available in the air system. As a result, machine productivity is compromised.